This proposal aims at developing a technique to obtain morphometric (quantitative) information on non-randomly distributed structures of lung from histological slides at the light microscopic level. This is necessary in the lung because of the converging nature of conducting structures. Existing morphometric data on the gas-exchange parenchyma are based on random samples and therefore do not account for acinar or lobular arrangements nor for systematic changes inside these structures (f.i. between proximal and distal areas). This problem is relevant to gas exchange problems and to exposure to airborne pollutants, as well as to the distribution of blood flow in aveolar capillaries. The proposal involves development of a semi-automatic device for the purpose of gathering information from video images of serial sections by means of a light pen with additional manual input of data; while structure recognition and outlining of boundaries will be done by an investigator subsequent data processing will be fully automatic. This set up will make possible processing of a very high amount of sections with moderate effort. Once developed, the first application of the instrument will be to reconstruct and quantitatively describe the structure of the terminal airways (acinus) in terms of number of branches, length and diameter of alveolar septa, alveolar ducts and sacs from the center toward the periphery of the acinus. Additional studies will include origin of the pulmonary venules and location of septal pleats with corner vessels in specific locations.